Does Gonadotropin Type Influence Mid Stimulation [Day 5/6] Serum FSH levels? A Retrospective Comparison of HMG and rFSH

Objectives: The primary aim of this study was to compare the serum follicle stimulating hormone (FSH) on stimulation day 5 or 6 when patients are stimulated with recombinant FSH (rFSH) or human menopausal gonadotropin (HMG). The secondary objective was to compare the absolute rise in serum FSH from baseline to day 5/6 of stimulation [delta FSH] between the two drugs. Material and Methods: Controlled ovarian hyperstimulation was started on the second or third day of the menstrual cycle with rFSH or HMG as per the clinician’s judgement. Patients took injections in the evening between 8–10 pm, and blood collection for serum FSH measurement was done in the morning of the day of stimulation start (baseline FSH) and again on day 5 or 6 [Day 5/6 FSH] of stimulation. Data was collected from the software Vrepro and patients’ medical records. Results: Initial analysis included 272 patients (204 in the HMG group and 68 in the rFSH group), with significant imbalances in gonadotropin dosing. After propensity score matching of 68 patients in each group, baseline characteristics (age, BMI, protocol distribution, gonadotropin doses) were well balanced between the groups. Despite similar baseline FSH levels (7.0 vs. 7.0 IU/L; p = 0.836), patients receiving rFSH achieved significantly higher day 5/6 FSH levels compared to those receiving HMG (19.6 vs. 15.5 IU/L; p <0.001), with a correspondingly higher absolute FSH increase (12.6 vs. 7.6 IU/L; p <0.001) and percentage increase (180.4 vs. 118.2%; p <0.001) Conclusion: Our analysis demonstrates that serum FSH level on day 5/6 of IVF stimulation is significantly higher when patients are stimulated with rFSH than HMG, with a correspondingly higher absolute increase from baseline.